Abstract: The invention is a self-aligning cementitious block and a wall system of such blocks stacked and joined by mortar to form a vertically oriented wall structure, where the block comprises alignment means which correctly align the block relative to the blocks upon which it is stacked such that the side walls are parallel to the side walls of the lower blocks. The alignment means comprise tongue members and groove members of corresponding configuration, where the tongue members preferably extend downward from the two end walls and the middle wall a distance below the lower edges of the side walls, and where the groove members are positioned on the tops of the end walls and middle wall, the groove members of inferior or lower blocks receiving the tongue members of a superior or upper block stacked thereupon. Starter blocks with a flat underside and corner blocks are also provided.

Abstract: The invention is a self-aligning cementitious block and a wall system of such blocks stacked and joined by mortar to form a vertically oriented wall structure, where the block comprises alignment features which correctly align the block relative to the blocks upon which it is stacked such that the side walls are parallel to the side walls of the lower blocks. The alignment features comprise projection members and recess members of corresponding configuration, where the projection members preferably extend downward from the two end walls and the middle wall a distance below the lower longitudinal edges of the side walls, and where the recess members are positioned on the tops of the end walls and middle wall, the recess members of inferior or lower blocks receiving the projection members of a superior or upper block stacked thereupon. Starter blocks with a flat underside and corner blocks are also provided.